Work vehicles such as agricultural and industrial tractors are frequently operated in less than ideal environmental conditions. For example, tractors are operated in uncomfortably warm or cold weather, and in dusty conditions caused by the work being done by the vehicle. As a result, it is desirable to provide in the cab a system for filtering and conditioning the air. One approach has been to place the components of an HVAC system in a housing in the tractor cab roof. This may result in a cumbersome structure which does not optimize the available space and may intrude into the cab area. Additionally, the ducts, hoses, conduits, wiring and inlet and outlet vents may be positioned based upon available space rather than efficient ergonomic placement.
One approach to overcoming these disadvantages has involved the use of one piece roto-molded roof structures which have a well or compartment to receive the HVAC units and have air ducts and vents molded into the roof structure. Such attempts have created their own disadvantages. For example, roto-molded parts do not have a high degree of dimensional stability and thus present a number of fit, mount-up and aesthetic difficulties. Further, one piece designs present less cost effective servicing access.
A two-piece vehicle roof structure having an integrated HVAC system is shown in U.S. Pat. No. 6,780,097. The lower roof member has contours and apertures for components of an HVAC system, and define air passages. In the two-piece vehicle roof structure described in the above patent, air intake apertures are located at the outer periphery of the lower roof member, on the left and right sides. Additionally, conditioned air vents are positioned on the left and right sides of the lower roof member, spaced inwardly from the intakes. Partition walls along the left and right sides of the lower roof member separate the unconditioned air ducts from the conditioned air ducts, and ensure that unconditioned air is passed through, rather than around, the HVAC core. The upper roof member encloses the unconditioned air ducts and the core chamber, and duct covers also may enclose the conditioned air ducts.
There is a need for a tractor roof structure with HVAC ducts having smaller space requirements than the two-piece vehicle roof structure described above. There is a need for a tractor roof structure with HVAC ducts that is low in cost, requires few components, and minimizes the use of separate divider walls.